Turbocharger with at least one variable turbine geometry turbine

ABSTRACT

The invention relates to a turbocharger for a combustion engine, in particular of a motor vehicle, with at least one variable turbine geometry turbine, which exhibits a rotor disk and vanes arranged on a vane support, which are spaced apart from each other around the rotor disk in at least one circumferential area, and with an adjuster to select the angular setting of the vanes. It is provided that the vanes ( 6 ) are fixed securely to the vane support ( 5 ), and exhibit different angular settings (α 1, α2, α3 ) relative to the rotor disk ( 3 ) in varying sectors ( 8, 9, 10 ) of the circumferential area ( 7 ), wherein the turbine ( 2 ) exhibits a cover device ( 12 ) that can rotate relative to the vane support ( 5 ) with at least one opening ( 14, 20 ) in its jacket surface ( 16 ) for purposes of sector selection.

The invention relates to a turbocharger for a combustion engine, in particular of a motor vehicle, with at least one variable turbine geometry turbine, which exhibits a rotor disk and vanes arranged on a vane support, which are spaced apart from each other around the rotor disk in at least one circumferential area.

PRIOR ART

A turbocharger with at least one variable turbine geometry-turbine (VTG-turbine) is known in the art. To this end, the turbine designed as a radial turbine exhibits an annular array of vanes spaced apart from each other and arranged concentrically around the rotor disk, which are arranged on a vane support. These vanes are responsible for guiding the flow on the rotor disk. The vanes are arranged on the vane support so that they can pivot around bearing arrangements and are swiveled by an adjuster for selecting the angular setting of the vanes. The angular setting of the vane supports relative to a flowing direction of an exhaust gas stream driving the turbine is selected by turning an adjuster relative to the vane support, e.g., an adjustment ring. Turning the adjustment ring swivels the vanes swivels the vans around the bearing devices. In this case, an angular setting optimal for the respective operating stage of the combustion engine can here be established or regulated.

To ensure that the vanes can be adjusted in the entire temperature range of the exhaust gas stream, high requirements must be placed on the fit of the bearing devices of the vanes, which in turn is associated with high manufacturing costs. The gap between the vanes and a casing of the turbine brought about by the principle of pivoting capability additionally provide for secondary flows, and hence losses in efficiency. In addition, soot may build up in the gaps, thereby blocking the adjustment mechanism.

All efforts notwithstanding, conventional VTG turbines can only be used up to about 830° C. Use at a higher exhaust gas stream temperature, for example in a combustion engine designed as a spark ignition engine, can only be realized with a significant outlay. Form a thermodynamic standpoint, another disadvantage to the swiveling and adjustment mechanism of the known VTG turbine described above is that the ends of the vanes facing the rotor disk move further and further away from the rotor disk with increasing swiveling angles. This results in a deterioration of inflow, and hence efficiency losses.

DISCLOSURE OF THE INVENTION

To reduce the number of rotating/pivoting parts for varying the turbine geometry, it is provided that the vanes be immovably fixed to the vane support, and exhibit varying angular settings relative to the rotor disk in different sectors of the circumferential area, wherein the turbine for sector selection exhibits a cover device that can turn relative to the vane support and has at least one opening in its jacket surface. The opening here preferably extends from the inner circumference to the outer circumference of the cover device. The angular setting for the used vanes is selected through sector selection via the opening in the cover device, which releases the selected sector with the vanes to be used, wherein the vanes not to be used are covered from the remaining cover device. The few reciprocally rotating parts provided for selecting the angular setting makes it possible to use the turbine at high exhaust gas stream temperatures. The turbine is a variable turbine geometry turbine (VTG-turbine). All vanes within a sector ensure an identical inflow (an identical inflow angle) for the rotor disk. The vanes fixed in place (relative to the vane support) can be designed as simpler vane profiles by comparison to conventional VGT-turbines, since they do not have to be separately pivoted. In particular, the VGT-turbine is a VGT-radial turbine.

In an advantageous embodiment of the invention, the vanes comprise a vane ring that circumferentially envelops the rotor disk. The vane ring is divided into the sectors with varying angular settings for the vanes. The cover device with opening mounted so that it can rotate relative to the vane ring is arranged around the vane ring. The vane ring is securely (rigidly) arranged in the turbine in a preferred embodiment.

It is advantageously provided that the vanes extend from an inner circumferential area of the cover device to an outer circumferential area of the vane. The secure (rigid) vanes continuously guide the exhaust gas stream up to a vane inlet on the outer circumference of the vane.

In an advantageous embodiment of the invention, the sectors exhibit a uniform expansion. This yields a uniform rotational angle for changing the angular setting of the vanes.

In particular, the circumferential expansion of the opening essentially corresponds to the circumferential expansion of the sectors. This makes the rotational angles for changing the angular setting of the vanes especially short.

Further advantageously provided is that the cover device be formed or partially formed by a casing of the turbine. In this embodiment, the vane support is twisted relative to the casing for sector selection.

As an alternative, the cover device is preferably designed as a separate sleeve or separate adjustment ring. This sleeve or adjustment ring is pivoted, and releases a sector on the nozzle ring with its opening (recess), depending on the rotational angle.

In an advantageous embodiment of the invention, the cover device exhibits several openings and in particular several identically designed, mutually allocated sectors. Mutually allocated sectors of the vane ring are situated in accordance with the arrangement of openings. These mutually allocated sectors of varying circumferential areas preferably exhibit vanes with the same angular setting.

Finally, it is advantageously provided that a minimal gap is formed between the ends of the vanes in the outer circumferential area of the rotor disk and the rotor disk. This gap between the ends of the vanes of the vane ring in the outer circumferential area of the rotor disk and the outer circumference of the rotor disk is hence minimal, as prescribed by the manufacturing tolerances for the turbine components.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail below based on the accompanying drawings. Shown on:

FIG. 1 is a variable turbine geometry turbine, the cover device of which exhibits an opening, and on

FIG. 2 is a variable turbine geometry turbine, the cover device of which exhibits two openings.

EMBODIMENT(S) OF THE INVENTION

FIG. 1 shows a turbine 2 of a combustion engine turbocharger, which is designed as a radial turbine 1, and exhibits variable turbine geometry. A vane ring 4 is arranged around a rotor disk 3 of the turbine 2, which is formed by vanes 6 spaced apart from each other. FIG. 1 shows only one circumferential area 7 of the vane ring 4. The vane ring 4 is divided into several sectors 8, 9, 10, of which only three sectors 8, 9, 10 are shown in the circumferential area 7 depicted on FIG. 1. The vanes 6 of each sector 8, 9, 10 exhibit a uniform angular setting α1, α2, α3 relative to the respective radial extension of the rotor disk 3. The first sector 8 has a first angular setting α1, the second sector 9 a second angular setting α2, and the third sector 10 a third angular setting α3. The number of vanes 6 is identical for each sector 8, 9, 10.

A cover device 12 designed as a sleeve 11 with an opening 14 designed as a recess 13 is arranged around the vane ring 4, The opening 14 extends from an inner circumference 15 to an outer circumference 15′ of a jacket surface 16 of the cover device 12. The cover device 12 is pivoted (dual arrow 17), and releases one of the sectors 8, 9, 10 on the vane ring 4 with its opening 14 depending on a (selected) rotational angle set by way of an adjustment mechanism (not shown) (hence the first sector 8 on FIG. 1). The circumferential expansion of the opening 14 essentially corresponds to the circumferential uniform expansion the sectors 8, 9, 10. Each of the vanes 6 extends from the inner circumference 15 of the jacket surface of the cover device 12 up to an outer circumferential area 18 of the rotor disk 3.

The following function results for the depicted arrangement to change the turbine geometry of turbine 2: One of the angular settings α1, α2, α3 of the used vane supports 5 is selected by choosing a sector 8, 9, 10 (sector selection) via the opening 14 in the cover device 12, which releases the selected sector 8, 9, 10 with the vanes 6 to be used, wherein the vanes 6 of the other sectors 8, 9, 10 not to be used are covered by the rest of the cover device 12. The few reciprocally rotating parts 4, 12 provided for selecting the angular setting enables the use of the turbine 2 even at high temperatures of an exhaust gas stream driving the turbine.

The turbine 2 on FIG. 2 essentially corresponds to the turbine 2 on FIG. 1, so that only the differences will be discussed here. The turbine 2 with variable turbine geometry exhibits a cover device 12 designed as an adjustment ring 19 with two opposing openings 14, 20. Mutually allocated first sectors 8, 21 with angular setting α1 and mutually allocated second sectors 9, 22 with angular setting α2 of the vane ring 4 are situated in accordance with the arrangement of openings 14, 20. These mutually allocated sectors 8, 21; 9, 22 of varying circumferential areas 7, 23 exhibit vanes 6 with identical angular settings α1, α2. The mutually allocated first sectors 8, 21 induce a radial inflow of the rotor disk 3, and enable a high throughput of exhaust gas. The mutually allocated second sectors 9, 22 enable a tangential inflow of the rotor disk 3, and a high flow rate of the exhaust gas. The following applies: α1<<α2.

Several (two here) openings 14, 20 place a more uniform load over the entire circumference of the rotor disk 3 during operation.

The number n of sectors 8, 9, 10 of varying angular setting α1, α2, . . . , αn (different sectors 8, 9, 10) is freely selectable (with n≧1). The number m of mutually allocated sectors 8, 21; 9, 22 is also freely selectable (with m≧1). Mutually allocated sectors 8, 21; 9, 22 preferably exhibit identical angular settings, and are in particular identically designed.

A gap 24 arising between the ends 25 of the vanes 3 of the vane ring 4 in the outer circumferential area 18 of the rotor disk 3 and outer circumference of the rotor disk 3 is minimal, as stipulated by the manufacturing tolerances for the turbine components. 

1. A turbocharger for a combustion engine comprising: at least one variable turbine-geometry turbine, including a rotor disk, a vane support, and vanes arranged on the vane support, which are spaced apart around the rotor disk, at least in a circumferential area for defining at least one sector; and a cover device having a jacket surface, wherein the cover device rotates relative to the vane support, and at least one opening is included in the jacket surface for selecting a sector; wherein the vanes are fixed securely to the vane support, and exhibit different angular settings relative to the rotor disk in varying sectors of the circumferential area. 2-9. (canceled)
 10. The turbocharger according to claim 1, wherein the vanes create a vane support that circumferentially envelops the rotor disk.
 11. The turbocharger according to claim 1, wherein the vanes extend from an inner circumference of the cover device to an outer circumference of the rotor disk.
 12. The turbocharger according to claim 1, wherein the sectors include a uniform expansion.
 13. The turbocharger according to claim 1, wherein a circumferential expansion of the opening corresponds to a circumferential expansion of the sectors.
 14. The turbocharger according to claim 1, wherein the cover device is at least partially created by a casing of the turbine.
 15. The turbocharger according to claim 1, wherein the cover device is designed as one of a separate sleeve and a separate adjustment ring.
 16. The turbocharger according to claim 1, wherein the cover device includes several openings and the turbocharger includes at least two generally identically designed, mutually allocated sectors.
 17. The turbocharger according to claim 1, wherein a minimal gap is created between ends of the vanes in an outer circumferential area of the rotor disk and an outer circumference of the rotor disk.
 18. The turbocharger according to claim 10, wherein the vanes extend from an inner circumference of the cover device to an outer circumference of the rotor disk.
 19. The turbocharger according to claim 10, wherein the sectors include a uniform expansion.
 20. The turbocharger according to claim 10, wherein a circumferential expansion of the opening corresponds to a circumferential expansion of the sectors.
 21. The turbocharger according to claim 10, wherein the cover device is at least partially created by a casing of the turbine.
 22. The turbocharger according to claim 10, wherein the cover device is one of a separate sleeve and a separate adjustment ring.
 23. The turbocharger according to claim 10, wherein the cover device includes several openings and the turbocharger includes at least two generally identically designed, mutually allocated sectors.
 24. The turbocharger according to claim 10, wherein a minimal gap is created between ends of the vanes in an outer circumferential area of the rotor disk and an outer circumference of the rotor disk.
 25. The turbocharger according to claim 11, wherein the sectors include a uniform expansion.
 26. The turbocharger according to claim 11, wherein a circumferential expansion of the opening corresponds to a circumferential expansion of the sectors.
 27. The turbocharger according to claim 11, wherein the cover device is at least partially created by a casing of the turbine.
 28. The turbocharger according to claim 11, wherein the cover device is one of a separate sleeve and a separate adjustment ring. 